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====== ffmpeg - Video - Resize - Maintain aspect ratio ======

<code bash>
-vf scale=1920:-1
-vf scale=-1:1080
-vf scale=1920:-2
-vf scale=-2:1080
</code>

<WRAP info>
**NOTE:**

  * **-1** for the width or height will keep it in ratio to the other specified dimension.
  * **-2** will keep it in ratio to the other specified dimension, but, to ensure it is divisible by 2 (a requirement for certain encodings such as yuv420p) the width or height will be adjusted if necessary.

</WRAP>

----

===== Example =====

<code bash>
ffmpeg -i input.mp4 -vf "scale=1920:-1" -c:a copy output.mp4
</code>

<WRAP info>
**NOTE:**  The **-1** tells ffmpeg to automatically calculate the height while maintaining the aspect ratio after sizing to the new width.

  * **-i input.mp4**: Specifies the input video file.
  * **-vf "scale=1920:-1"**: Applies the scale filter to resize the video width to 1920 pixels, and the video height is calculated to ensure the aspect ratio is maintained.
  * **-c:a copy**: Copies the media streams without re-encoding.
  * **output.mp4**: Name of the output file.

</WRAP>